[PATCH] Add FilteredArgList to represent filtered arglist

[David Blaikie]

On May 25, 2013 3:22 PM, "Rui Ueyama" <ruiu at google.com> wrote:
>
> With this patch we can write a loop for command line options like this
>
>   for (const auto &arg : args->filter(OPT_SOMETHING)
>     ...
>
> instead of
>
>   for (auto it = args->filtered_begin(OPT_SOMETHING),
>          ie = args->filtered_end(); it != ie; ++it) {
>     ...
>
> I plan to use this in lld in where range-based for loop is allowed.
>
> http://llvm-reviews.chandlerc.com/D867
>
> Files:
>   include/llvm/Option/ArgList.h
>   lib/Option/ArgList.cpp
>
> Index: include/llvm/Option/ArgList.h
> ===================================================================
> --- include/llvm/Option/ArgList.h
> +++ include/llvm/Option/ArgList.h
> @@ -22,6 +22,7 @@
>  namespace opt {
>  class Arg;
>  class ArgList;
> +class FilteredArgList;
>  class Option;
>
>  /// arg_iterator - Iterates through arguments stored inside an ArgList.
> @@ -137,10 +138,14 @@
>    const_reverse_iterator rbegin() const { return Args.rbegin(); }
>    const_reverse_iterator rend() const { return Args.rend(); }
>
> +  FilteredArgList filter(OptSpecifier Id0 = 0U, OptSpecifier Id1 = 0U,
> +                         OptSpecifier Id2 = 0U) const;
> +
>    arg_iterator filtered_begin(OptSpecifier Id0 = 0U, OptSpecifier Id1 =
0U,
>                                OptSpecifier Id2 = 0U) const {
>      return arg_iterator(Args.begin(), *this, Id0, Id1, Id2);
>    }
> +
>    arg_iterator filtered_end() const {
>      return arg_iterator(Args.end(), *this);
>    }
> @@ -275,6 +280,31 @@
>    /// @}
>  };
>
> +/// FilteredArgList - ArgList with filters. Useful to be used in
> +/// range-based for loop to iterate over filtered arguments.

Could we just have/use a generic range abstraction (essentially a simple
class template with two iterator members, one returned by begin, the other
by end) rather than writing a custom type here?

> +class FilteredArgList {
> +private:
> +  FilteredArgList(const ArgList &) LLVM_DELETED_FUNCTION;
> +  void operator=(const ArgList &) LLVM_DELETED_FUNCTION;
> +
> +public:
> +  FilteredArgList(const ArgList &_Args, OptSpecifier _Id0 = 0U,
> +                  OptSpecifier _Id1 = 0U, OptSpecifier _Id2 = 0U)
> +    : Args(_Args), Id0(_Id0), Id1(_Id1), Id2(_Id2) {}
> +
> +  arg_iterator begin() {
> +    return Args.filtered_begin(Id0, Id1, Id2);
> +  }
> +
> +  arg_iterator end() {
> +    return Args.filtered_end();
> +  }
> +
> +private:
> +  const ArgList &Args;
> +  OptSpecifier Id0, Id1, Id2;
> +};
> +
>  class InputArgList : public ArgList  {
>  private:
>    /// List of argument strings used by the contained Args.
> Index: lib/Option/ArgList.cpp
> ===================================================================
> --- lib/Option/ArgList.cpp
> +++ lib/Option/ArgList.cpp
> @@ -44,6 +44,11 @@
>    Args.push_back(A);
>  }
>
> +FilteredArgList ArgList::filter(OptSpecifier Id0, OptSpecifier Id1,
> +                                OptSpecifier Id2) const {
> +  return FilteredArgList(*this, Id0, Id1, Id2);
> +}
> +
>  void ArgList::eraseArg(OptSpecifier Id) {
>    for (iterator it = begin(), ie = end(); it != ie; ) {
>      if ((*it)->getOption().matches(Id)) {
>
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